JP3807945B2

JP3807945B2 - Method and apparatus for treating organic wastewater

Info

Publication number: JP3807945B2
Application number: JP2001080807A
Authority: JP
Inventors: 琢也小林; 甬生葛; 俊博田中
Original assignee: Ebara Corp
Current assignee: Ebara Corp
Priority date: 2001-03-21
Filing date: 2001-03-21
Publication date: 2006-08-09
Anticipated expiration: 2021-03-21
Also published as: JP2002273466A

Description

【０００１】
【発明の属する技術分野】
本発明は、汚水処理に関するもので、特に廃水の生物処理に伴う余剰汚泥の生成量の削減に関するものであり、かつ活性汚泥の固液分離に関するものであり、有機性工場廃水や生活排水の処理に用いることができる有機性廃水の処理方法及び装置に関する。
【０００２】
【従来の技術】
有機性廃水の生物処理において、廃水中の窒素やリンの除去のために生物処理槽を、攪拌のみを行う嫌気槽と曝気を行う好気槽に分け、嫌気槽流出液を好気槽に供給し、好気槽流出液の一部を沈殿池に送って上澄水を処理水として得ると共に、好気槽流出液の他の一部を、嫌気槽へ循環する処理が実用化されている。例えば、廃水中の窒素除去にこの方法を適用した場合、好気槽ではＢＯＤ酸化菌による廃水中の有機物の酸化分解の他に、活性汚泥中の硝化菌によりアンモニア性窒素は硝酸に酸化される。好気槽から流出した液の一部である活性汚泥混合液が嫌気槽に入ると、嫌気槽で活性汚泥混合液中の硝酸性窒素を、活性汚泥中の脱窒菌が原水に含まれる有機物を用い窒素に還元する。以上の工程により廃水中のアンモニア性窒素は、気体窒素に還元され廃水中から除去される。
【０００３】
一方、活性汚泥法などの生物処理において、その処理工程で処理水を得るためには、汚泥混合液から活性汚泥の固液分離を行わなければならない。通常では、汚泥混合液を沈殿池に流入させ、重力沈降により活性汚泥を沈降させ、上澄水を処理水として沈殿池から流出させる方法が用いられる。しかし、この場合活性汚泥を沈降させるため、十分な広い沈降面積および長い滞留時間を有する沈殿池が必要であり、処理装置の大型化と設置容積の増大要因のとなっている。また、活性汚泥がバルキングなどにより沈降性が悪化した場合、沈殿池より汚泥が流出し、処理水の悪化を招く。
【０００４】
近年、沈殿池に変わる活性汚泥の固液分離方法として、好気槽に不織布や織布などの通水性シートからなるろ過体を浸漬させ、水頭圧でろ過水を得る方法が知られている。この場合、ろ過体表面に沿って活性汚泥混合液を流すことによりろ過体表面に形成される汚泥のダイナミックろ過層による分離で、清澄なろ過水が得られる。ろ過流束低下時には、ろ過体下部に設置した散気管により曝気することにより、層の厚さが増したダイナミックろ過層を剥離し、ダイナミックろ過に適したろ過層を再形成することにより、安定した流束が得られるとしている。
【０００５】
【発明が解決しようとする課題】
しかしながら、上記の従来の有機性廃水の生物処理においては、近年閉鎖性水域などでの水質悪化が問題となっており、従来行われてきた有機物類の除去だけでなく窒素などの除去も必要とされている。固液分離のためには大きな面積と滞留時間を有する沈殿池が必要であり、処理装置の大型化と設置容積が増大する原因となっている。また、活性汚泥の沈降性が悪化した場合には沈殿池より処理水と共に活性汚泥が流出し、処理水の悪化の原因となっている。沈殿池の代わりに、ダイナミックろ過槽を設置した場合、沈殿池から返送汚泥を送るための返送ラインと返送ポンプが不要となる。その代わり、ダイナミックろ過を行うために、ろ過体表面に活性汚泥混合液を流すために、循環ポンプが新たに必要となるため、結局ポンプやラインの数は変わらないことになる。
【０００６】
本発明は、上記の問題点を解決するもので、嫌気＋好気の活性汚泥処理プロセスにおいて、容易に清澄なろ過水が得られるダイナミックろ過のできるろ過分離槽を設置することで安定したろ過水が得られ、さらに嫌気＋好気の活性汚泥処理プロセスの好気槽から嫌気槽への循環ラインの途中にダイナミックろ過槽を設置し、ろ過体表面の活性汚泥混合液を流すためのポンプや、好気槽から嫌気槽への循環ラインとしてのポンプなどに要するポンプの数を減らして、ポンプやラインの数を削減し、省エネルギー効果が期待できる処理方法および装置を提供する。また、本発明は、その際窒素除去もできる有機性廃水の処理方法および装置を提供する。
【０００７】
【課題を解決するための手段】
本発明者等は、前記の課題より、高い膜透過流束と、良好な処理水質を安定して得ることと共に、原水に含まれる窒素成分を十分に除去する方法について種々研究した。
そして、生物処理後の活性汚泥と処理水との固液分離にダイナミックろ過を用い、かつろ過分離槽から流出する活性汚泥混合液を嫌気槽へ循環させれば、上記の要件を全て満たすことができることを見出した。
本発明は、このような知見に着目して完成されたものである。
【０００８】
本発明は、下記の手段により前記の課題を解決することができた。
（１）有機性廃水を嫌気槽に導入し、嫌気槽を経た後に好気槽に流入する有機性廃水の生物処理において、該好気槽から活性汚泥混合液を通水性ろ過体を浸漬、設置したろ過分離槽に供給し、該通水性ろ過体表面に汚泥のダイナミックろ過層を形成させ、ろ過水を得る一方、該ろ過分離槽から流出した活性汚泥混合液を上記嫌気槽に返送することを特徴とする有機性廃水の処理方法。
（２）前記有機性廃水は、下水であることを特徴とする請求項１記載の有機性廃水の処理方法。
（３）前記有機性廃水は、有機性工場廃水又は生活排水であることを特徴とする請求項１又は請求項２記載の有機性廃水の処理方法。
（４）有機性廃水を導入する嫌気槽、前記嫌気槽からの液を導入する好気槽、通水性ろ過体を浸漬、設置されてなり、前記好気槽からの活性汚泥混合液が導入されて、通水性ろ過体表面に沿って流れ、通水性ろ過体表面にダイナミックろ過層を形成させ、ろ過水を得るろ過分離槽と、該ろ過分離槽からの流出活性汚泥混合液を前記嫌気槽に返送させる配管を具備することを特徴とする有機性廃水の処理装置。
【０００９】
本発明の嫌気槽と好気槽を含む生物処理法としては、嫌気無酸素好気法、生物的リン除去法などが含まれる。
嫌気・好気の過程による脱窒素法では、窒素を含有する有機性廃水は嫌気槽において好気槽から循環されるＮＯ₂イオンを含有する硝化液（活性汚泥混合液の一部）と混合されて脱窒素の反応が行われ、嫌気槽の液は次に好気槽に送られ、好気性条件でＢＯＤ成分の生物学的分解と窒素成分の硝化が行われている。このため、従来の脱窒素法では好気槽から嫌気槽への硝化液の循環が不可欠であって、そのための液の循環ラインとそのためのポンプが必要としていた。
本発明では、嫌気槽と好気槽の後にダイナミックろ過層を形成するろ過分離槽を設け、ろ過分離槽の液を嫌気槽に送り、循環させることにより、前記液がＮＯ₂イオンを含有されるために、嫌気槽と好気槽で硝化・脱窒素を行うことができることが分かった。そして、この方法によれば、従来の好気槽から嫌気槽への硝化液の循環を行わなくても硝化・脱窒素を行うことができるので、硝化液の循環のためのラインとそのためのポンプが不要である。
【００１０】
【発明の実施の形態】
以下に、本発明の実施の形態を図面を参照して詳細に説明する。
図１は、本発明の処理方法により下水を処理する一実施例のフローシートを示す。
図１に示すように、本処理装置は嫌気槽と好気槽、ろ過分離槽、処理水槽からなる。下水１は、嫌気槽８又は好気槽９のいずれかに供給することができるが、図１の場合嫌気槽８に供給される。嫌気槽８では活性汚泥の沈降を防ぎ、槽内を均一に保つため攪拌機１２により攪拌を行う。嫌気槽８から流出した嫌気槽流出液２は好気槽９に供給される。好気槽９では槽内の攪拌と活性汚泥への酸素供給のため、曝気用ブロワ１８より散気管１３へ空気を供給し好気槽９の攪拌を行う。好気槽９から流出した好気槽流出液３は、好気槽流出液循環ポンプ１６によりろ過分離槽１０に供給される。
【００１１】
ろ過分離槽１０の下側より供給された好気槽流出液３は、通水性ろ過体１５の表面を上昇しながら、通水性ろ過体１５よりろ過され、ろ過された水は取水管２３、ろ過水ラインバルブ２０を経てろ過水４を得る。この時、通水性ろ過体１５表面における好気槽流出液３の平均流速が、通水性ろ過体１５に対し汚泥沈降速度以上０．０５ｍ／ｓ未満であることが望ましい。また、ろ過はろ過分離槽１０と取水管２３出口の間の水頭差を利用することが望ましい。ろ過水４は処理水槽１１に供給され、処理水槽１１からのオーバーフローを処理水７として得る。
一方、ろ過分離槽１０から流出した活性汚泥混合液は、循環液５として嫌気槽８へ返送、循環させられる。
なお、この循環液５の流れは、好気槽流出液循環ポンプ１６の１個の働きにより行うことができる。すなわち、この処理系において、嫌気槽８から好気槽９への嫌気槽流出液２の流れ及びろ過分離槽１０から嫌気槽８への活性汚泥混合液の流れを、各槽の液を次の槽へ水位差で送り込む方式を採用すれば、好気槽流出液循環ポンプ１６は、好気槽９からの好気槽流出液３をろ過分離槽１０へ送るだけの作用によって、この処理系全体の循環流を送る働きをすることができる。このため、処理系全体についての液の輸送を省エネルギーで行うことができる。
【００１２】
通水性ろ過体１５の洗浄は、一定時間ごとにろ過を停止し、ろ過水ラインバルブ２０を閉じ、空洗ブロワ１９よりろ過分離槽１０の下部より曝気し、生じた上向流により通水性ろ過体１５表面の洗浄を行う。その後、洗浄水ラインバルブ２１および洗浄排水ラインバルブ２５を開にして、処理水槽１１からろ過水４を洗浄水ポンプ１７により通水性ろ過体１５へ逆流させ、膜内部に浸入した汚泥などを除去する。洗浄後は、洗浄水ポンプ１７を停止、洗浄水ラインバルブ２１及び洗浄排水ラインバルブ２５を閉、ろ過水ラインバルブ２０を開にし、再び通常のろ過運転を行う。
【００１３】
【実施例】
以下において、本発明を実施例によりさらに具体的に説明するが、本発明は、この実施例により限定されるものではない。
【００１４】
実施例１
この実施例１においては、図１に示すようなフローにより団地下水の処理を行った。
団地下水は、嫌気槽８と好気槽９からなる生物処理槽に供給され、好気槽９からの好気槽流出液３はろ過分離槽１０の下部から供給される。ろ過分離槽１０内部では好気槽流出液の流れが均一になるように整流板を設けてある。ろ過分離槽１０内部に設置された通水性ろ過体１５により好気槽流出液はろ過され、ろ過水４を得る。ろ過水４は、ろ過分離槽１０と取水管２３の水頭差によりろ過される。
第１表に、生物処理槽の運転条件を示す。
【００１５】
【表１】

【００１６】
第１表に示すように、本実施例の生物処理槽の容積は好気槽２ｍ³、嫌気槽１ｍ³であり、生物処理槽への原水流入量は１６ｍ³／ｄであった。ＭＬＳＳは約３０００ｍｇ／リットルであり、良好な汚泥沈降性であった。ろ過分離槽を除いた生物処理槽全体に対するＢＯＤ負荷は、約０．１３ｋｇ／ｋｇ・ｄとなった。好気槽からろ過分離槽を経て嫌気槽に循環する循環流量は、３２ｍ³／ｄに設定した。
【００１７】
なお、本実施例は本発明の一例である。流入原水ＢＯＤが、生物反応槽において完全分解除去されるＢＯＤ負荷であることが、本発明の効果を一層高める。ろ過分離槽を除いた生物処理槽のＢＯＤ負荷を、０．３ｋｇ／ｋｇ・ｄとするのが望ましい。この場合、ろ過分離槽に流入する好気槽流出液中に、原水に由来するＢＯＤが残留しないことから、ろ過体表面での生物膜形成が抑制され、長期にわたり安定した運転を行うことができる。
【００１８】
第２表に、通水性ろ過体の処理条件を示す。本実施例では、縦横それぞれ１．１ｍ、厚さ１０ｍｍ、ろ過体有効表面積２ｍ²のろ過体モジュールを４枚用いた。ろ過体モジュール４枚の合計有効面積は８ｍ²となる。織布にはポリエステル系繊維の織布を用いた。ろ過時の平均水頭差は、約１０ｃｍであった。
【００１９】
【表２】

【００２０】
ろ過体の洗浄は、最初ろ過水ラインバルブ２０を閉じ、空洗用ブロワ１９からの空気を、散気管１４より送り空洗を２分間行う。その後、洗浄水ラインバルブ２１および洗浄排水ラインバルブ２５を開け、ろ過水を洗浄水ポンプ１７よりろ過体モジュール内に送り、逆流洗浄を２分間行う。これにより、ろ過体モジュール内部に入り込んだ汚泥を、ろ過体モジュール外へ排出することができ、定常ろ過時の水質の悪化を抑えることができる。逆流洗浄終了後、洗浄水ラインバルブ２１および洗浄排水ラインバルブ２５を閉、ろ過水ラインバルブ２０を開に定常ろ過を開始する。その後３時間ろ過運転を行った後、再び上記洗浄工程を行うことにより、ろ過水量を回復させた。上記の定常ろ過と洗浄工程を行いながら、約２ヶ月間の連続運転を行った。この時の原水と処理水の平均水質を第３表にまとめて示す。
【００２１】
【表３】

【００２２】
第３表に、処理結果を示す。原水のｐＨが７．５、濁度１２０度、ＳＳ５６．１ｍｇ／リットルであるのに対し、処理水はｐＨ７．６、濁度４．１度、ＳＳ９．６ｇ／リットルであり、通水性ろ過体によるろ過で清澄な処理水を得ることができた。また、ＢＯＤについて原水７２．０ｍｇ／リットルに対し処理水５ｍｇ／リットル以下、ＣＯＤについて原水４４．７ｍｇ／リットルに対し処理水９．８ｍｇ／リットルと良好な処理水を得ることができた。
さらに、アンモニア性窒素（ＮＨ₄-Ｎ）について原水１７．９ｍｇ／リットルに対し処理水０．１ｍｇ／リットル以下とほぼ完全に硝化され、全窒素（Ｔ−Ｎ）について原水２５．７ｍｇ／リットルに対し処理水８．２ｍｇ／リットルと、全窒素の３分の１を除去することができた。
【００２３】
図２に、本実施例におけるろ過流束の時間経過を示す。初期ろ過から約３時間経過してもろ過流束の低下が少なく、約２ｍ／ｄ以上を維持でき、安定した処理が行えた。
図３に、本実施例での処理水濁度の経過を示す。ろ過開始から１０分後には濁度は１０度以下となり、その後３０分以降は濁度５度以下で安定しており、ろ過体表面に汚泥のダイナミックろ過槽が短時間で形成し、安定処理したことが認められた。
【００２４】
【発明の効果】
本発明によれば、有機性の工場廃水や生活排水の処理において、生物処理後の活性汚泥と処理水との固液分離に、ダイナミックろ過を用いることにより、精密ろ過や限外ろ過と比較し、高い膜透過流束による膜分離が可能となり、ろ過分離槽に必要な面積を削減できる可能性がある。また、固液分離に膜分離法を用いることにより、沈殿池と比較して良好な処理水水質を安定して得ることが期待できる。
また、活性汚泥混合液を、好気槽からろ過分離槽を経て嫌気槽へ循環させるため、原水に含まれる窒素成分を除去することができる。従来の好気槽から硝化液を嫌気槽へ循環させる手段が不要となり、循環ライン及びポンプが省略でき、省エネルギーに貢献する。
【図面の簡単な説明】
【図１】本発明の有機性廃水の処理装置の一実施例のフローシートである。
【図２】本発明の一実施例の経過時間とろ過流束の関係を示すグラフである。
【図３】本発明の一実施例の経過時間と処理水濁度の関係を示すグラフである。
【符号の説明】
１下水
２嫌気槽流出液
３好気槽流出液
４ろ過水
５循環液
６洗浄水
７処理水
８嫌気槽
９好気槽
１０ろ過分離槽
１１処理水槽
１２攪拌機
１３散気管
１４散気管
１５通水性ろ過体
１６好気槽流出液循環ポンプ
１７洗浄水ポンプ
１８曝気用ブロワ
１９空洗用ブロワ
２０ろ過水ラインバルブ
２１洗浄水ラインバルブ
２２排泥管
２３取水管
２４洗浄排水ライン
２５洗浄排水ラインバルブ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to sewage treatment, and particularly relates to reduction of the amount of surplus sludge produced by biological treatment of wastewater, and to solid-liquid separation of activated sludge, and treatment of organic factory wastewater and domestic wastewater. The present invention relates to a method and an apparatus for treating organic wastewater that can be used for water.
[0002]
[Prior art]
In biological treatment of organic wastewater, the biological treatment tank is divided into an anaerobic tank that performs only agitation and an aerobic tank that performs aeration in order to remove nitrogen and phosphorus in the wastewater, and the anaerobic tank effluent is supplied to the aerobic tank. In addition, a part of the aerobic tank effluent is sent to a sedimentation basin to obtain supernatant water as treated water, and another part of the aerobic tank effluent is circulated to an anaerobic tank. For example, when this method is applied to nitrogen removal from wastewater, ammonia nitrogen is oxidized to nitric acid by nitrifying bacteria in activated sludge in addition to oxidative decomposition of organic matter in wastewater by BOD oxidizing bacteria in an aerobic tank. . When activated sludge mixed liquid, which is part of the liquid flowing out from the aerobic tank, enters the anaerobic tank, nitrate nitrogen in the activated sludge mixed liquid is contained in the anaerobic tank, and organic matter containing denitrifying bacteria in the activated sludge is contained in the raw water. Use reduced to nitrogen. Through the above process, ammoniacal nitrogen in the wastewater is reduced to gaseous nitrogen and removed from the wastewater.
[0003]
On the other hand, in biological treatment such as the activated sludge method, in order to obtain treated water in the treatment step, it is necessary to perform solid-liquid separation of activated sludge from the sludge mixed solution. Usually, a method is used in which a sludge mixed solution is flowed into a sedimentation basin, activated sludge is sedimented by gravity sedimentation, and the supernatant water is discharged from the sedimentation basin as treated water. However, in this case, the activated sludge is settled, so that a sedimentation basin having a sufficiently large sedimentation area and a long residence time is required, which is a factor for increasing the size of the processing apparatus and increasing the installation volume. Moreover, when activated sludge deteriorates sedimentation property by bulking etc., sludge flows out from a sedimentation basin and causes deterioration of treated water.
[0004]
In recent years, as a method for solid-liquid separation of activated sludge that is replaced by a sedimentation basin, a method is known in which a filter body made of a water-permeable sheet such as a nonwoven fabric or a woven fabric is immersed in an aerobic tank to obtain filtered water with water head pressure. In this case, clear filtered water is obtained by separating the sludge formed on the surface of the filter body by the dynamic filtration layer by flowing the activated sludge mixed liquid along the surface of the filter body. When the filtration flux is lowered, aeration is performed by an aeration tube installed at the bottom of the filter body, so that the dynamic filtration layer with an increased layer thickness is peeled off, and the filtration layer suitable for dynamic filtration is re-formed. It is said that flux can be obtained.
[0005]
[Problems to be solved by the invention]
However, in the biological treatment of the above conventional organic wastewater, the deterioration of water quality in closed water areas has become a problem in recent years, and it is necessary to remove not only organic substances that have been conventionally performed but also removal of nitrogen and the like. Has been. For solid-liquid separation, a sedimentation basin having a large area and residence time is required, which causes an increase in the size and installation volume of the processing apparatus. Moreover, when the sedimentation property of activated sludge deteriorates, activated sludge flows out from a sedimentation basin with treated water, and causes the deterioration of treated water. If a dynamic filtration tank is installed instead of a settling basin, a return line and a return pump for sending return sludge from the settling basin are not required. Instead, in order to perform the dynamic filtration, a circulating pump is newly required to flow the activated sludge mixed liquid on the surface of the filter body, so that the number of pumps and lines does not change after all.
[0006]
The present invention solves the above-mentioned problems. In an anaerobic + aerobic activated sludge treatment process, stable filtered water is provided by installing a filtration separation tank capable of dynamic filtration that can easily obtain clear filtered water. In addition, a dynamic filtration tank is installed in the middle of the circulation line from the aerobic tank to the anaerobic tank in the anaerobic + aerobic activated sludge treatment process, and a pump for flowing the activated sludge mixed liquid on the surface of the filter body, Provided is a processing method and apparatus that can reduce the number of pumps required for a pump as a circulation line from an aerobic tank to an anaerobic tank, reduce the number of pumps and lines, and expect an energy saving effect. The present invention also provides a method and apparatus for treating organic wastewater that can also remove nitrogen.
[0007]
[Means for Solving the Problems]
The present inventors have studied various methods for sufficiently removing nitrogen components contained in raw water while stably obtaining a high membrane permeation flux and good treated water quality from the above problems.
And if dynamic filtration is used for solid-liquid separation of activated sludge and treated water after biological treatment and the activated sludge mixed liquid flowing out from the filtration separation tank is circulated to the anaerobic tank, all of the above requirements can be satisfied. I found out that I can do it.
The present invention has been completed by paying attention to such knowledge.
[0008]
The present invention has solved the above-described problems by the following means.
(1) Introducing organic wastewater into an anaerobic tank, and immersing and installing an activated sludge mixed liquid through the aerobic tank in biological treatment of organic wastewater flowing into the aerobic tank after passing through the anaerobic tank A sludge dynamic filtration layer is formed on the surface of the water-permeable filter body to obtain filtered water, and the activated sludge mixed liquid flowing out of the filtration separation tank is returned to the anaerobic tank. A method for treating organic wastewater.
(2) The organic wastewater treatment method according to claim 1, wherein the organic wastewater is sewage.
(3) The organic wastewater treatment method according to claim 1 or 2, wherein the organic wastewater is organic factory wastewater or domestic wastewater.
(4) Anaerobic tank for introducing organic waste water, an aerobic tank for introducing liquid from the anaerobic tank, a water-permeable filter is immersed and installed, and the activated sludge mixed liquid from the aerobic tank is introduced. The filtration separation tank that flows along the surface of the water-permeable filter body, forms a dynamic filtration layer on the surface of the water-permeable filter body, and obtains filtered water; and the activated sludge mixed liquid flowing out from the filtration separation tank is supplied to the anaerobic tank. An organic wastewater treatment apparatus comprising a return pipe.
[0009]
Examples of the biological treatment method including the anaerobic tank and the aerobic tank of the present invention include an anaerobic anaerobic anaerobic method, a biological phosphorus removal method and the like.
In the denitrification method by anaerobic and aerobic processes, organic wastewater containing nitrogen is mixed with nitrification liquid (part of the activated sludge mixture) containing NO ₂ ions circulated from the aerobic tank in the anaerobic tank. The denitrification reaction is performed, and the liquid in the anaerobic tank is then sent to the aerobic tank, where biological decomposition of the BOD component and nitrification of the nitrogen component are performed under aerobic conditions. For this reason, in the conventional denitrification method, circulation of the nitrification liquid from the aerobic tank to the anaerobic tank is indispensable, and a liquid circulation line for that purpose and a pump for that purpose are required.
In the present invention, the filtration separation tank to form a dynamic filtration layer after anaerobic tank and an aerobic tank provided, the feed liquid filtration separation tank anaerobic tank by circulating the liquid is contained NO ₂ ion Therefore, it was found that nitrification and denitrification can be performed in an anaerobic tank and an aerobic tank. And according to this method, since nitrification and denitrification can be performed without performing circulation of nitrification liquid from a conventional aerobic tank to an anaerobic tank, a line for circulation of nitrification liquid and a pump therefor Is unnecessary.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the drawings.
FIG. 1 shows a flow sheet of one embodiment for treating sewage by the treatment method of the present invention.
As shown in FIG. 1, this processing apparatus consists of an anaerobic tank, an aerobic tank, a filtration separation tank, and a treated water tank. The sewage 1 can be supplied to either the anaerobic tank 8 or the aerobic tank 9, but is supplied to the anaerobic tank 8 in the case of FIG. In the anaerobic tank 8, the activated sludge is prevented from settling and stirred by the stirrer 12 to keep the inside of the tank uniform. The anaerobic tank effluent 2 flowing out from the anaerobic tank 8 is supplied to the aerobic tank 9. In the aerobic tank 9, the aerobic tank 9 is agitated by supplying air from the aeration blower 18 to the air diffuser 13 for stirring in the tank and supplying oxygen to the activated sludge. The aerobic tank effluent 3 flowing out from the aerobic tank 9 is supplied to the filtration separation tank 10 by the aerobic tank effluent circulation pump 16.
[0011]
The aerobic tank effluent 3 supplied from the lower side of the filtration separation tank 10 is filtered from the water-permeable filter 15 while rising on the surface of the water-permeable filter 15, and the filtered water is filtered through the water intake pipe 23 and the filtration. The filtered water 4 is obtained through the water line valve 20. At this time, it is desirable that the average flow rate of the aerobic tank effluent 3 on the surface of the water-permeable filter 15 is greater than or equal to the sludge settling speed and less than 0.05 m / s with respect to the water-permeable filter 15. In addition, it is desirable to use a water head difference between the filtration separation tank 10 and the outlet of the intake pipe 23 for the filtration. The filtered water 4 is supplied to the treated water tank 11, and the overflow from the treated water tank 11 is obtained as treated water 7.
On the other hand, the activated sludge mixed liquid flowing out from the filtration separation tank 10 is returned to the anaerobic tank 8 and circulated as the circulating liquid 5.
The circulating fluid 5 can be flowed by one function of the aerobic tank effluent circulating pump 16. That is, in this treatment system, the flow of the anaerobic tank effluent 2 from the anaerobic tank 8 to the aerobic tank 9 and the flow of the activated sludge mixed liquid from the filtration separation tank 10 to the anaerobic tank 8 If a system in which the water level is fed into the tank is adopted, the aerobic tank effluent circulation pump 16 simply sends the aerobic tank effluent 3 from the aerobic tank 9 to the filtration / separation tank 10, and this entire processing system. It can work to send a circulating flow of. For this reason, the transport of the liquid about the whole processing system can be performed with energy saving.
[0012]
Washing of the water-permeable filter 15 stops filtration at regular intervals, closes the filtered water line valve 20, aerates from the lower part of the filtration separation tank 10 from the air-washing blower 19, and performs water-permeable filtration by the generated upward flow. The surface of the body 15 is cleaned. Thereafter, the washing water line valve 21 and the washing drain line valve 25 are opened, and the filtered water 4 is caused to flow backward from the treated water tank 11 to the water-permeable filter 15 by the washing water pump 17 to remove sludge and the like that have entered the membrane. . After the washing, the washing water pump 17 is stopped, the washing water line valve 21 and the washing drain line valve 25 are closed, the filtrate water line valve 20 is opened, and normal filtration operation is performed again.
[0013]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the examples.
[0014]
Example 1
In Example 1, the groundwater was treated according to the flow shown in FIG.
The groundwater is supplied to a biological treatment tank composed of an anaerobic tank 8 and an aerobic tank 9, and the aerobic tank effluent 3 from the aerobic tank 9 is supplied from the lower part of the filtration separation tank 10. A flow regulating plate is provided in the filtration separation tank 10 so that the flow of the aerobic tank effluent is uniform. The effluent from the aerobic tank is filtered by the water-permeable filter 15 installed inside the filtration separation tank 10 to obtain filtered water 4. The filtered water 4 is filtered by the head difference between the filtration separation tank 10 and the intake pipe 23.
Table 1 shows the operating conditions of the biological treatment tank.
[0015]
[Table 1]

[0016]
As shown in Table 1, the volume of the biological treatment tank of the present embodiment is the aerobic tank 2m ^3, an anaerobic tank 1 m ^3, the raw water inflow into the biological treatment tank was 16m ³ / d. MLSS was about 3000 mg / liter, and the sludge sedimentation was good. The BOD load on the entire biological treatment tank excluding the filtration separation tank was about 0.13 kg / kg · d. The circulation flow rate circulating from the aerobic tank to the anaerobic tank through the filtration / separation tank was set to 32 m ³ / d.
[0017]
This embodiment is an example of the present invention. The inflow raw water BOD is a BOD load that is completely decomposed and removed in the biological reaction tank, which further enhances the effect of the present invention. The BOD load of the biological treatment tank excluding the filtration separation tank is preferably set to 0.3 kg / kg · d. In this case, since BOD derived from raw water does not remain in the aerobic tank effluent flowing into the filtration separation tank, biofilm formation on the surface of the filter body is suppressed, and stable operation can be performed over a long period of time. .
[0018]
Table 2 shows the treatment conditions for the water-permeable filter. In this example, four filter modules each having a length and width of 1.1 m, a thickness of 10 mm, and a filter effective surface area of 2 m ² were used. The total effective area of the four filter body modules is 8 m ² . A polyester fiber woven fabric was used as the woven fabric. The average water head difference at the time of filtration was about 10 cm.
[0019]
[Table 2]

[0020]
In order to wash the filter body, the filtered water line valve 20 is first closed, the air from the air washing blower 19 is sent from the air diffuser 14 and air washing is performed for 2 minutes. Thereafter, the washing water line valve 21 and the washing drain line valve 25 are opened, the filtrate is sent from the washing water pump 17 into the filter module, and the backwashing is performed for 2 minutes. Thereby, the sludge which entered the inside of a filter body module can be discharged | emitted out of a filter body module, and the deterioration of the water quality at the time of regular filtration can be suppressed. After the backwashing is completed, the washing water line valve 21 and the washing drain line valve 25 are closed and the filtered water line valve 20 is opened to start steady filtration. Then, after performing a filtration operation for 3 hours, the amount of filtered water was recovered by performing the above washing step again. While performing the above-described steady filtration and washing steps, continuous operation was performed for about 2 months. Table 3 summarizes the average water quality of the raw water and treated water at this time.
[0021]
[Table 3]

[0022]
Table 3 shows the processing results. The pH of the raw water is 7.5, the turbidity is 120 degrees, and the SS is 56.1 mg / liter, whereas the treated water is pH 7.6, the turbidity is 4.1 degrees, and the SS is 9.6 g / liter. A clear treated water could be obtained by filtration through the above. In addition, as for BOD, the treated water was 5 mg / liter or less with respect to the raw water 72.0 mg / liter, and the treated water was 9.8 mg / liter with respect to the raw water 44.7 mg / liter with respect to the COD.
Furthermore, ammonia nitrogen (NH ₄ -N) was nitrified almost completely at 0.1 mg / liter or less of treated water against 17.9 mg / liter of raw water, and total nitrogen (TN) was reduced to 25.7 mg / liter of raw water. On the other hand, 8.2 mg / liter of treated water and 1/3 of the total nitrogen could be removed.
[0023]
In FIG. 2, the time passage of the filtration flux in a present Example is shown. Even after about 3 hours from the initial filtration, there was little decrease in the filtration flux, it was possible to maintain about 2 m / d or more, and a stable treatment could be performed.
FIG. 3 shows the progress of the treated water turbidity in this example. Ten minutes after the start of filtration, the turbidity is 10 degrees or less, and after 30 minutes, the turbidity is stable at 5 degrees or less, and a sludge dynamic filtration tank is formed on the surface of the filter body in a short time and stabilized. It was recognized that
[0024]
【The invention's effect】
According to the present invention, in the treatment of organic factory wastewater and domestic wastewater, dynamic filtration is used for solid-liquid separation between activated sludge and treated water after biological treatment, compared with microfiltration and ultrafiltration. Membrane separation by high membrane permeation flux becomes possible, and the area required for the filtration separation tank may be reduced. Moreover, by using a membrane separation method for solid-liquid separation, it can be expected that a good quality of treated water can be stably obtained as compared with a sedimentation basin.
Moreover, since the activated sludge mixed liquid is circulated from the aerobic tank to the anaerobic tank through the filtration separation tank, the nitrogen component contained in the raw water can be removed. The conventional means for circulating the nitrification liquid from the aerobic tank to the anaerobic tank is not required, and the circulation line and the pump can be omitted, contributing to energy saving.
[Brief description of the drawings]
FIG. 1 is a flow sheet of one embodiment of an organic wastewater treatment apparatus of the present invention.
FIG. 2 is a graph showing the relationship between elapsed time and filtration flux in one embodiment of the present invention.
FIG. 3 is a graph showing the relationship between elapsed time and treated water turbidity in one example of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Sewage 2 Anaerobic tank effluent 3 Aerobic tank effluent 4 Filtration water 5 Circulating liquid 6 Washing water 7 Treated water 8 Anaerobic tank 9 Aerobic tank 10 Filtration separation tank 11 Treated water tank 12 Stirrer 13 Aeration pipe 14 Aeration pipe 15 Water permeability Filter 16 Aerobic tank effluent circulation pump 17 Washing water pump 18 Aeration blower 19 Air washing blower 20 Filtration water line valve 21 Washing water line valve 22 Drainage pipe 23 Intake pipe 24 Washing drainage line 25 Washing drainage line valve

Claims

In organic treatment of organic wastewater that introduces organic wastewater into an anaerobic tank and flows into the aerobic tank after passing through the anaerobic tank, filtration separation is performed by immersing the activated sludge mixed liquid from the aerobic tank and installing it. A sludge dynamic filtration layer is formed on the surface of the water-permeable filter body to obtain filtered water, and the activated sludge mixed liquid flowing out of the filtration separation tank is returned to the anaerobic tank. Organic wastewater treatment method.

The method for treating organic wastewater according to claim 1, wherein the organic wastewater is sewage.

The organic wastewater treatment method according to claim 1 or 2, wherein the organic wastewater is organic factory wastewater or domestic wastewater.

An anaerobic tank for introducing organic waste water, an aerobic tank for introducing liquid from the anaerobic tank, and a water-permeable filter are immersed and installed, and the activated sludge mixed liquid from the aerobic tank is introduced and passed through. A filtration separation tank for flowing along the surface of the aqueous filter body, forming a dynamic filtration layer on the surface of the water filtration filter body to obtain filtered water, and a pipe for returning the effluent activated sludge mixed liquid from the filtration separation tank to the anaerobic tank An organic wastewater treatment apparatus comprising: